Bounds on bearing and symbol estimation with side information

We develop Cramer-Rao bounds (CRBs) for bearing, symbol, and channel estimation of communications signals in flat-fading channels. We do this using the constrained CRB formulation of German and Hero (1990), and Stoica and Ng (see IEEE Signal Processing Lett., vol.5, p.177-79, 1998), with the unknown parameters treated as deterministic constants. The equality constraints may be combined arbitrarily, e.g., we may develop CRBs for bearing estimation of constant modulus (CM) signals where a subset of the symbols are known (semi-blind, CM case). The results establish the value of side information in a large variety of communications scenarios. We focus on the CM and semi-blind properties and develop closed-form CRBs for these cases. Examples are presented indicating the relative value of the training and CIM property. These show the significant amount of signal processing information provided under these two conditions. In addition, we consider the performance of the maximum-likelihood beamformer for the semi-blind case, assuming the bearings are known. This semi-blind beamformer achieves the appropriate (constrained) CRB with finite data at finite SNR. Analysis also reveals that in a semi-blind scenario with two closely spaced sources, ten or more training symbols are sufficient to achieve the asymptotic training regime. Together with previous results on angle estimation for known sources, these results indicate that relatively few training samples enable both angle estimation and closely spaced co-channel source separation that approaches the CRB with finite data and finite SNR     

A model for diffraction-limited high-power multimode fiberamplifiers using seeded stimulated Brillouin scattering phaseconjugation

Diffraction-limited polarized stimulated Brillouin scattering (SBS) Stokes output from a multimode fiber is possible when the Stokes beam is the phase conjugate of diffraction-limited polarized pump light from a narrow-band master oscillator. Net amplification can be obtained by interposing a gain medium, such as a fiber amplifier between the master oscillator and the region of SBS generation. This paper proposes and studies numerically a model which describes the space-time dynamics of SBS generation, including phase conjugation, attenuation, phonon decay, thermal noise, inhomogeneous broadening, and amplifier gain. Noise reduction and phase locking are obtained by seeding the low-power end of the fiber at the Stokes frequency. Simulations are described for the case of 1.064 μm light amplification in a dual-clad Yb-doped multimode fiber amplifier     

Highly Efficient,Solution‐Processed,Single‐Layer,Electrophosphorescent Diodes and the Effect of Molecular Dipole Moment

A new family of highly soluble electrophosphorescent dopants based on a series of tris‐cyclometalated iridium(III) complexes (1–4) of 2‐(carbazol‐3‐yl)‐4/5‐R‐pyridine ligands with varying molecular dipole strengths have been synthesized. Highly efficient, solution‐processed, single‐layer, electrophosphorescent diodes utilizing these complexes have been prepared and characterized. The high triplet energy poly(9‐vinylcarbazole) PVK is used as a host polymer doped with 2‐(4‐biphenylyl)‐5‐(4‐tert‐butyl‐phenyl)‐1,3,4‐oxadiazole (PBD) for electron transport. Devices with a current efficiency of 40 cd A^?1 corresponding to an EQE of 12% can thus be achieved. The effect of the type and position of the substituent (electron‐withdrawing group (CF₃) and electron‐donating group (OMe)) on the molecular dipole moment of the complexes has been investigated. A correlation between the absorption strength of the singlet metal‐to‐ligand charge‐transfer (¹MLCT) transition and the luminance spectral red shift as a function of solvent polarity is observed. The strength of the transition dipole moments for complexes 1–4 has also been obtained from TD‐DFT computations, and is found to be consistent with the observed molecular dipole moments of these complexes. The relatively long lifetime of the excitons of the phosphorescence (microseconds) compared to the charge‐carrier scattering time (less than nanoseconds), allows the transition dipole moment to be considered as a “quasi permanent dipole”. Therefore, the carrier mobility is sufficiently affected by the long‐lived transition dipole moments of the phosphorescent molecules, which are randomly oriented in the medium. The dopant dipoles cause positional and energetic disorder because of the locally modified polarization energy. Furthermore, the electron‐withdrawing group CF₃ induces strong carrier dispersion that enhances the electron mobility. Therefore, the strong transition dipole moment in complexes 3 and 4 perturbs both electron and hole mobilities, yielding a reduction in exciton formation and an increase in the device dark current, thereby decreasing the device efficiency.     

Prediction of total intake of dry matter and net energy in a lactation

Daily records on DM intake, net energy intake, and milk yield from 191 Holstein cows in six herds were used to study the differences in accuracy and precision among different methods of estimating total DM intake during a lactation. In using cumulative measures of intake from partial lactations to predict total intake, accuracy reached 85% at 100 d postpartum. Measurements of intake taken around midlactation gave better predictions of total intake than those taken during other periods of lactation. Methods were evaluated for estimating total feed intake during a lactation based on data collected intermittently and separated by either equal or unequal intervals throughout the lactation. The average percentage of bias across all sampling schemes was 6% or less of actual intake. Six of the seven sampling schemes using only 10 d of intake information throughout the lactation had correlations with actual intake of .97 or higher. For equally spaced methods, both accuracy and precision of estimation increased with increased frequency of sampling. For unequally spaced methods, accuracy increased with sampling frequency after 150 d in milk. Total milk production was used to predict feed intake during a lactation. Milk yield alone accounted for 37 and 33% of the variation of total intake using actual and estimated yields, respectively.     

Effect of tray liners on the drip loss of lamb chops during retail display

The amount of drip lost by lamb chops during display was affected by the type of tray liner used. In one study involving chilled and frozen/thawed meat, the use of an absorbent paper liner increased the drip loss and influenced whether or not the quantity of drip was affected by freezing/thawing. In another study, thawed chops held for 24 h on plastic coated trays without liner or on a plastic coated liner had less than 2% drip loss, whereas adjacent chops from the same loin processed and held in the same way but displayed on liners of absorbent paper or paper pouches of diatomaceous earth lost 4·3% and 5·6% drip, respectively. This effect of the material in contact with the meat should be considered when reporting drip loss data and when comparing results with those of other researchers.     

Thawing of lamb loin chops in air and CO(2). Effect on colour and drip

Colour retention and drip loss was assessed during retail display for chilled lamb chops displayed fresh or stored in CO(2) for 7 weeks before display, and for chops frozen for various times and thawed in air or CO(2). A sensory panel found fresh lamb chops to have an acceptable display life of 1 day, while chops which had been frozen for 1 day and then thawed lasted 2 days. Holding chops for 7 weeks in a CO(2) atmosphere at - 1·5°C improved display life to 3 days, but frozen chops held for 7 weeks before thawing had deteriorated in colour, and only one group was acceptable on the initial day of display. Initially there were no differences in Hunter L values (brightness) due to treatment, but chilled chops or those frozen for 1 day showed a greater increase in L values by the second day than those frozen for 7 weeks, after which there was no change in brightness. Hunter a values (redness) were higher in chilled chops and those thawed after 1 day's frozen storage than those frozen for 7 weeks before thawing. Hunter b values (yellowness) were greater at all times in chilled chops held for 7 weeks and varied amongst the other treatments. The measured per cent drip from chops frozen for only 1 day was greater on thawing than drip from chops frozen for 7 weeks before thawing. Drip during display, assessed by a sensory panel, increased more in those chops stored either chilled or frozen for 7 weeks before display.     

Quantum-efficiency measurements in oxygen-containing gallium lanthanum sulphide glasses and fibers doped with Pr/sup 3+/

The production of competitive fiber amplifiers in the 1.3-/spl mu/m region requires both good quantum efficiency in the lasing ion and the capability to produce low-loss fibers. Oxygen-doped gallium lanthanum sulphide (GLS) doped with Pr/sup 3+/ may provide a route to both, We describe measurements of the quantum efficiency of Pr/sup 3+/ emission at 1.3 /spl mu/m from the /sup 1/G/sub 4/-/sup 3/H/sub 5/ transition in GLS glass and fiber containing varying quantities of lanthanum oxide. We show that oxide-containing GLS glasses, which are known to have considerably better thermal and glass-forming properties than pure GLS, can show quantum efficiencies of up to 84% of that of pure GLS, No degradation of quantum efficiency is seen when oxide-containing GLS glass is pulled into fiber form.     

Series-system reliability-estimation using very small binomialsamples

This investigation explored the effect of incorporating prior information into series-system reliability estimates, where the inferences are made using very small sets (less than 10 observations) of binomial test-data. To capture this effect, the performance of a set of Bayes interval estimators was compared to that of a set of classical estimators over a wide range of subsystem beta prior-distribution parameters. During a Monte Carlo simulation, the Bayes estimators tended to provide shorter interval estimators when the mean of the prior system-reliability differed from the true reliability by 20 percent of less, but the classical estimators dominated when the difference was greater. Based on these results, the authors conclude that there is no clear advantage to using Bayes interval estimation for sample sizes less than 10 unless the poor mean system reliability is believed to be within 20 percent of the true system reliability. Otherwise, the Lindstrom-Madden estimator, a useful classical alternative for very small samples, should be used     

Gain enhancement of multistage parametric intracavity frequencyconversion

Multistage intracavity frequency conversion in optical parametric oscillators (OPOs) can generate new frequencies efficiently over a large dynamic range of pump intensity. These frequencies can be either higher or lower than the pump frequency. High efficiency is correlated with steady states exhibiting nearly complete pump depletion (CPD). Placing a second OPO crystal with high small-signal gain in the cavity does not affect the steady states with CPD, if the pump is depleted and the idler out-coupled before these fields reach the high-gain crystal. However, the high-gain crystal promotes rapid saturation, and hence higher time-averaged efficiency, in Q-switched devices. Numerical modeling of injection-seeded Q-switched devices in three spatial dimensions suggests that excellent beam quality at high peak power is obtainable. However, instabilities can occur in this modeling, and it is not known if these numerical instabilities entail instabilities in the physical devices